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Golf Cart Motor Speed Sensor: The Basics

A golf cart motor speed sensor is, in simplest terms, a device which detects or reads the rpm of the motor and transmits this information to the speed controller to control various motor functions. A golf cart motor speed sensor can be mechanical, electrical, or magnetic based. We’ll discuss several different types, how they operate, why they are needed and symptoms when they fail.

In the golf cart industry, both DC and AC motors are now used. A golf cart motor speed sensor is not needed with DC series wound motors since they do not utilize many features of separately excited shunt wound motors, such as regenerative (regen) braking or roll away protection. Most, but not all, DC powered separately excited motors have a golf cart motor speed sensor. This device communicates the motor rpm to the controller, where regen braking and the roll away features can be controller.

Regenerative braking is a method used to make the motor act as a generator to governor the golf cart’s speed to a preset rpm, as well use the power generated to slightly recharge the batteries. Thus the need to know the motor rpm is evident so the controller can control such features.

The roll away feature is purely for safety. If you forget to set the parking brake on your golf cart and it starts to roll away, this feature will limit it to only be able to roll in neutral at a preset rpm, which is usually the equivalent of under ½ a MPH or so. This allows you to easily catch up to the cart before it crashes into something causing major damage.

In the case of a golf cart motor speed sensor employed on AC motors, the same principles apply. All AC motors must utilize a speed sensor to control the motor properly and offer such features as regen braking and the roll away feature offered in separately excited DC motors.

Many golf cart motor speed sensors employ an electromagnetic power to “read” the motor rpm. Generally, there is a magnet present in the closed end of the motor as well as the sensor itself which reads how the magnet is reacting with the magnetic field inside the motor. This style is very prevalent used with separately excited shunt wound DC golf cart motors.

Another golf cart motor speed sensor type is mechanical based. This type of sensor uses a disk with slots in it, which passes by an eye or reader head. Depending on how many slots are read per minute translate into a calculation within the speed controller to determine motor rpm. The speed sensor seen here is used on all of our AC golf cart power conversion systems.

The last golf cart motor speed sensor type we’ll mention is both mechanical and electrical. The EZGO RXV 48V golf cart uses a 3-phase AC induction motor made by Iskra in Slovenia. In the earlier models, from 2008-2010, the motor used a bearing type sensor on the outside end plate of the motor before the motor brake disk. The revolutions of this bearing sent an electrical signal to the motor to interpret the motor rpm. In later models, after 2010, this sensor was changed to a different version.

Typically, in a golf cart which uses a motor speed sensor, there are some classic symptoms to look for which indicate a bad sensor. If the cart is creeping along slowly, erratic speed, or shuttering similar to a low voltage or bad battery situation, you may have a bad golf cart motor speed sensor. For specific tests for your brand, make and model, always consult your dealer or service manual.

Sounds like a timing issue. You might have to look behind the flywheel at the pulser / pick-up coil. They are generally mounted onto a plate that where the coil reads the crank as it spins by to adjust the timing. The plate is usually attached with screws through slotted holes. You loosen the screws, then spin the plate one way or another. One direction advances the timing and the other retards it. I suspect those screws may have loosened and the timing plate has moved allowing it to function better in one direction than another.